Project Category: Stormwater

The Town of Falmouth retained Tata & Howard to remediate lead-contaminated soil associated with historical firing range activities at a former gravel pit owned by the Town. Due to the gravel pit’s location within a current drinking water source area, the objective of the remediation was to restore the release to background and remove the potential threat to the underlying groundwater quality. In addition, the presence of estimated habitats of rare wildlife and priority habitats of rare species at the gravel pit required the filing of a Notice of Intent (NOI) with the Conservation Commission and implementing measures to protect the rare wildlife and species. Tata & Howard prepared a site-specific scope of work for bidding purposes and managed all the field activities. Part of the remedial action plan was to screen the soil in an effort to remove the lead bullets and facilitate disposal of the contaminated soil at a Massachusetts lined landfill. Analytical testing of the soil revealed that some areas contained leachable lead, which required stabilization with Portland cement prior to being transported to the landfill. During the excavation activities, Tata & Howard utilized a field portable x-ray fluorescence (XRF) analyzer to obtain real-time concentrations of lead in soil. Use of the XRF minimized contractor down time because decisions relative to the extent of excavation required could be made in the field. Confirmatory laboratory analytical results correlated well with the XRF data. Tata & Howard prepared a Permanent Solution with No Conditions Statement, which documents that a condition of No Significant Risk has been achieved at the Site and that the release conditions have been restored to background.

Tata & Howard provided engineering services for design, preparation of a hydrologic and hydraulic report, two easement maps, design submittals for DOT review, construction administration, and resident observation for the rehabilitation of the Great Brook Stormwater Stormwater Culvert under Cherry Street in Waterbury, CT. The project provided for the replacement of about 65 linear feet of the existing structurally deficient top to the Great Brook Stormwater Culvert under Cherry Street and adjacent private properties. The existing steel beams, corrugated metal arches, and bituminous concrete or concrete slabs forming the top of the culvert were removed and precast concrete beams were placed on elastomeric bearing pads to form the replacement culvert top. Additionally, about 50 linear feet of the existing eroded cobblestone bottom were removed to a minimum depth of 12 inches and replaced with reinforced cast in place concrete. Further, approximately 32 linear feet of undermined walls (16 linear feet on the west side and 16 linear feet on the east side) were excavated, with cast in place concrete placed below the existing culvert masonry walls. The interior culvert masonry walls within the project limits were also repointed. The work required the reconstruction of 30 feet of Cherry Street, the adjacent sidewalks, and approximately 750 square feet of a private gravel parking lot property. During construction, a water control system capable of conveying normal flow capacity of the Great Brook Stormwater Culvert at Cherry Street was maintained.

The Whitin Wellfield Water Treatment Facility design consisted of a pressure filtration vessel housed within a new pre-fabricated metal building, and upgrades to the chemical feed system housed within an existing building on site. The project also included associated electrical and instrumentation, as well as site stormwater management. The design called for replacement of the existing paved driveway, but since no new impervious pavement was added, the only stormwater runoff that required treatment was the rooftop runoff from the new building. MassDEP guidelines require treatment of runoff from metal roofed buildings within the Zone II radius of a wellfield. The necessary treatment was achieved by discharging the roof runoff into a grass-lined channel. The grass-lined channel provided pre-treatment for a bioretention area, which consisted of a shallow excavation in which specially selected metal-resistant grasses and shrubs were planted within a specific soil to provide treatment. This treatment train provided the necessary total suspended solids removal but did not receive credit for infiltration, which was required by MassDEP. The biofiltration area was designed to collect, store, and infiltrate a 100-year storm event, so although the BMP train did not receive credit by MassDEP standards, the local Conservation Commission agreed that runoff would be infiltrated and therefore approved the design.

Tata & Howard provided evaluation, design, construction administration, and resident observation services to the South Central Connecticut Regional Water Authority (SCCRWA) for the replacement of the Whitney-Wintergreen water storage tank. The project included an analysis of SCCRWA’s Whitney-Wintergreen service area to determine the appropriate volume of storage needed to serve its customers, and a 1 million gallon concrete tank was constructed to replace the existing 1.5 million gallon steel tank at the same site. The project also included demolition of the existing tank as well as stormwater management at the site. The project was completed in September of 2015.

The Long Pond Water Treatment Plant project consists of an 8.4 mgd DAF treatment plant, ozone contactors, and raw water pump station with intakes. The site stormwater management part of the project was separated into two designs: the parts of the site under the Conservation Commission’s jurisdiction and those that are not.

The majority of the site from the entrance along the access road and around the main treatment plant building did not fall under the Conservation Commission’s jurisdiction, and therefore did not require stormwater treatment. However, we did not want to ignore the potential impacts of stormwater, so this portion of the site was designed to allow for 100 percent infiltration. Along the access road, grading allowed for water to discharge and infiltrate in undeveloped areas where it will not impact the site. The area around the main building flows over land to an infiltration basin that is designed to collect, store, and infiltrate most storm events. There is an overflow in the case that the infiltration basin is overwhelmed during a large storm event.

The construction of the raw water pump station and intakes fell within the Conservation Commission’s and other agencies’ jurisdiction. Since the only impervious area was the building, and the building did not have a metal roof, MassDEP guidelines allowed for direct infiltration. The guidelines usually require the infiltration to occur in drywells in this situation, but the local Conservation Commission agreed that having an infiltration basin with an overflow would require fewer man-made structures and therefore have less impact on the surrounding environment. The infiltration was designed to store and infiltrate the raw water pump station roof runoff, and included an overflow for large storms.

The purpose of the MS4 annual report is to document the status of NPDES Storm Water Management Program (SWMP) implementation with information including the following:

A self-assessment review of compliance with the permit conditions;

An assessment of the appropriateness of the selected BMPs;

An assessment of the progress towards achieving the measurable goals;

A summary of results of any information that has been collected and analyzed;

A discussion of activities for the next reporting cycle;

A discussion of any changes in identified BMPs or measurable goals; and

Reference to any reliance on another entity for achieving any measurable goal.

Tata & Howard has provided MS4 Annual Report services to the following municipalities:

Dover, Massachusetts

Tata & Howard assists the Town of Dover, MA with MS4 compliance. Services have included completion of the annual report, facilitation of an educational training session with municipal leaders, review and updating of stormwater infrastructure, and education on the upcoming MS4 Permit. We are currently assisting them with preparing the Notice of Intent required for coverage under the new 2016 Massachusetts MS4 General Permit.

Manchester-by-the-Sea, Massachusetts

Tata & Howard reviewed stormwater information and provided a Year 11 annual report to the Town of Manchester-by-the-Sea, MA.

Leicester, Massachusetts

Tata & Howard assists the Town of Leicester, MA with MS4 compliance. Services have included creation of an IDDE program including written statement of IDDE responsibilities, outfall inspection and mapping, and educational presentation to Town leaders on illicit connections. In addition, Tata & Howard helped the Town create and pass a bylaw related to illicit connections required by the MS4 Permit and produced the MS4 Annual Report for the Town. We are currently assisting them with preparing the Notice of Intent required for coverage under the new 2016 Massachusetts MS4 General Permit. Moving forward, we will be assisting the Town with additional mapping and catchment area identification.

The Happy Hollow Chemical Feed Station design consisted of a small chemical feed building and equipment, well pump and water main installation, and associated utilities and site work. The only impervious surface on the site was the new building. Since building roof was a membrane and not metal and there was no paving, MassDEP guidelines allowed for direct infiltration of the stormwater runoff from the roof. This was accomplished by pitching the roof to one side and collecting the runoff into two 4” PVC drain pipes that discharged into an infiltration system consisting of four Cultec infiltration chambers. Since it was not feasible to install an overflow for these chambers, the infiltration system was designed based on a 100-year storm event in order to have the capacity to collect, store, and infiltrate the largest storms that the site could potentially encounter. The chemical feed building also housed a re-agentless chlorine analyzer that required a constant supply of sampling water and therefore produced a constant waste flow of clean water. This analyzer waste flow was also included in the sizing of the infiltration system.

Tata & Howard has provided the Town of Grafton, MA with extensive stormwater field engineering services. Services have included the completion of stormwater infrastructure mapping in accordance with the Massachusetts NPDES MS4 Permit, Illicit Discharge Detection and Elimination Program. Mapping services included outfalls and interconnections, manholes, catch basins piping, and establishment of catchment areas. Follow-up work will continue with outfall inspection, screening, and dry weather sampling.

Tata & Howard provided engineering services for Marlborough, MA for a redesign of the Town’s Public Works Facility. The work included a stormwater management design and program to reduce the contamination of stormwater runoff and prohibit illicit discharges as required by current regulations and as required by the latest draft MS4 permit. The project also included a proposed site plan showing the proposed drainage improvements for the site including new drainage system infrastructure, stormwater detention and treatment facilities, existing and proposed grade, and all building and features. The project also included an erosion control plan and drainage report appropriate for various environmental permitting submissions including and erosion control plan with boundaries of any resource areas and associated buffers. Lastly, Tata & Howard assisted with permitting assistance and obtaining Conservation Commission approval of the project.

Tata & Howard provides ongoing stormwater engineering services to the Town of Leicester, Massachusetts in support of their status as a NPDES Phase II Municipal Separate Storm System (MS4) community. Work involves outfall mapping and inspection, Illicit Discharge Detection and Elimination, development of Annual Reports, and compliance with documentation and reporting components of the MS4 Permit. In addition, Tata & Howard assisted the Town of Leicester Highway Department with mapping and inspection of stormwater outfalls and produced a unique record of each outfall, including photographs. Tata & Howard also developed a report summarizing the outfall inspections.